I am standing in line at the lunch buffet at my hospital and I have an option: a red meat steak entree or an eggplant parmesan. If each day I choose the red meat or a processed meat entree, I increase my chance of colorectal cancer by almost 20 percent. If I am standing in line at McDonalds, Wendy’s or Burger King and order a quarter pounder, it would increase my risk of colorectal cancer by over 50 percent.

On average, Americans eat 93 grams of red meat a day, taking account of the 5 percent of Americans who are vegetarians, (full disclosure: I am a vegetarian). This adds up to a colon cancer risk contributing to 84,000 excessive deaths worldwide from cancer due to processed and red meat.

Last week, a World Health Organization panel stated: Processed meats cause cancer and red meat probably raises the risk of cancer. If we eat 50 grams of red or processed meat (one hot dog or 6 pieces of bacon) each day, we increase our risk of colorectal cancer by 20 percent.

Declaring meat, a staple part of the American diet, as a carcinogen (cancer causing agent) is stunning. But we should have seen it coming. In 2007, the American Institute for Cancer Research, and in 2009 the National Institutes of Health, and in 2011 the World Cancer Research Fund International all pointed to the link between meat and cancer.

The WHO panel went further than the other studies. The panel categorized processed meat in the same risk group as cigarettes and red meat in the same risk group as mustard gas, as cancer-causing agents.

It’s partly unfair to say that we should look at processed meat as causing colorectal cancer just as we see cigarettes as causing lung cancer. Yes, both definitively cause cancer, but 50 grams a day of processed meat increases cancer risk by 20 percent while smoking increases risk of cancer by 2500 percent.

So how does processed or red meat cause cancer?

When we cook at home we add salt and pepper. When meat is processed, manufacturers add N-nitroso-compound and polycyclic aromatic hydrocarbons to hot dogs and bacon. (I took organic chemistry and still don’t know these compounds, but they certainly do not sound healthy.)

When baked, these agents transform into heterocyclic aromatic amines, and when they reach our colon they alter the DNA of the cells in the colon. It just takes one cell to mutate and grow uncontrollably to become cancer.

Often in scientific literature a cause and effect relationship between a behavior or food and a disease is hard to prove, and so it took 800 studies over decades to show this relationship.

So what can we do? The American culture is meat-based. An American meal is felt to be incomplete with no meat entree.

But things are changing. Since 1970, red meat consumption has declined from over 101 pounds per person per year to under 75 pounds, and vegetable consumption has increased. But, we still have a ways to go. We just have to make the right choice next time we are standing in line.